This project examines whether hormonal responses to training modulate (i.e. enhance or impair) memory processing by acting on peripheral and/or central biogenic amine systems. The results of a series of studies indicate that, if administered soon after training, subcutaneous injections of epinephrine, norepinephrine, or adrenocorticotrophic hormone (ACTH), can enhance or disrupt later retention performance. Further findings show that, across several behavioral and treatment conditions, retention performance is closely related to transient posttraining decreases in whole brain norepinephrine and adrenal epinephrine concentrations. This project is designed to confirm these early findings and to examine the generality of the view that hormonally mediated brain noradrenergic responses to training may modulate the storage of new information. In addition, the experiments examine the possibility that posttraining norepinephrine concentrations predict later retention performance in animals that receive other treatments (e.g., drugs, electrical stimulation of the brain) which impair or enhance memory storage processing. Furthermore, we are examining the possibility that the effects of many amnestic and memory-enhancing treatments are mediated by a common neurobiological mechanism that includes involvement of peripheral catecholamine systems. In these studies, we administer (intraperitoneal) adrenergic receptor blocking agents, prior to training and posttraining treatments that enhance or impair memory, in an attempt to attenuate the effects of these treatments on memory. Thus, the experiments in this project examine the possibility that endogenous peripheral and central adrenergic responses to training modulate memory processing. Also, the studies examine the role of adrenergic systems in mediating retrograde amnesia and memory enhancement.